docs: improve CLI help, shell completion, and README

- Add command groups (Getting Started, Search, Downloads, Daemon, System)
- Add shell completion command (bash, zsh, fish, powershell)
- Add flag completions for --type, --quality, --sort, --lang, --genre,
  --country, --method, --player
- Improve Long descriptions and Examples for all commands
- Split doctor disk check into platform-specific files (Unix/Windows)
- Validate infoHash length before truncating (prevent panic)
- Fix references to non-existent 'unarr daemon start' command
- Move stats command to System & Diagnostics group
- Rewrite README with complete documentation, correct config format
  (toml not yaml), all commands, shell completion section

internal/cmd/daemon_install.go

@@ -0,0 +1,239 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"text/template"
+
+	"github.com/fatih/color"
+	"github.com/spf13/cobra"
+)
+
+const systemdTemplate = `[Unit]
+Description=unarr download daemon
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart={{.BinPath}} start
+Restart=always
+RestartSec=10
+User={{.User}}
+Environment=HOME={{.Home}}
+
+[Install]
+WantedBy=multi-user.target
+`
+
+const launchdTemplate = `<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <key>Label</key>
+  <string>com.torrentclaw.unarr</string>
+  <key>ProgramArguments</key>
+  <array>
+    <string>{{.BinPath}}</string>
+    <string>start</string>
+  </array>
+  <key>RunAtLoad</key>
+  <true/>
+  <key>KeepAlive</key>
+  <true/>
+  <key>StandardOutPath</key>
+  <string>{{.LogDir}}/unarr.log</string>
+  <key>StandardErrorPath</key>
+  <string>{{.LogDir}}/unarr.err.log</string>
+</dict>
+</plist>
+`
+
+func newDaemonInstallCmdReal() *cobra.Command {
+	return &cobra.Command{
+		Use:   "install",
+		Short: "Install daemon as a system service (systemd/launchd)",
+		Long: `Install the unarr daemon as a system service so it starts automatically on boot.
+
+  Linux:  Creates a systemd user service (~/.config/systemd/user/unarr.service)
+          Enables lingering so the service runs without an active login session.
+  macOS:  Creates a launchd user agent (~/Library/LaunchAgents/com.torrentclaw.unarr.plist)
+
+The service is enabled and started immediately after installation.
+No sudo or root access is required (uses user-level service managers).`,
+		Example: `  unarr daemon install`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runDaemonInstall()
+		},
+	}
+}
+
+func newDaemonUninstallCmdReal() *cobra.Command {
+	return &cobra.Command{
+		Use:   "uninstall",
+		Short: "Remove daemon system service",
+		Long: `Stop the daemon and remove the system service created by 'unarr daemon install'.
+
+Removes the service file and disables automatic startup on boot.`,
+		Example: `  unarr daemon uninstall`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runDaemonUninstall()
+		},
+	}
+}
+
+type serviceData struct {
+	BinPath string
+	User    string
+	Home    string
+	LogDir  string
+}
+
+func runDaemonInstall() error {
+	binPath, err := os.Executable()
+	if err != nil {
+		return fmt.Errorf("find executable: %w", err)
+	}
+	binPath, _ = filepath.EvalSymlinks(binPath)
+
+	home, _ := os.UserHomeDir()
+	user := os.Getenv("USER")
+	if user == "" {
+		user = os.Getenv("USERNAME")
+	}
+
+	data := serviceData{
+		BinPath: binPath,
+		User:    user,
+		Home:    home,
+		LogDir:  filepath.Join(home, ".local", "share", "unarr"),
+	}
+
+	bold := color.New(color.Bold)
+	green := color.New(color.FgGreen)
+
+	fmt.Println()
+	bold.Println("  unarr daemon install")
+	fmt.Println()
+
+	switch runtime.GOOS {
+	case "linux":
+		return installSystemd(data, green)
+	case "darwin":
+		return installLaunchd(data, green)
+	default:
+		return fmt.Errorf("service installation not supported on %s yet", runtime.GOOS)
+	}
+}
+
+func installSystemd(data serviceData, green *color.Color) error {
+	// User-level systemd service (no sudo needed)
+	dir := filepath.Join(data.Home, ".config", "systemd", "user")
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return fmt.Errorf("create systemd dir: %w", err)
+	}
+
+	path := filepath.Join(dir, "unarr.service")
+	f, err := os.Create(path)
+	if err != nil {
+		return fmt.Errorf("create service file: %w", err)
+	}
+	defer f.Close()
+
+	tmpl := template.Must(template.New("systemd").Parse(systemdTemplate))
+	if err := tmpl.Execute(f, data); err != nil {
+		return fmt.Errorf("write service file: %w", err)
+	}
+
+	fmt.Printf("  Created: %s\n", path)
+
+	// Enable and start
+	exec.Command("systemctl", "--user", "daemon-reload").Run()
+	exec.Command("systemctl", "--user", "enable", "unarr").Run()
+	exec.Command("systemctl", "--user", "start", "unarr").Run()
+
+	// Enable lingering so user services run without login session
+	exec.Command("loginctl", "enable-linger", data.User).Run()
+
+	fmt.Println()
+	green.Println("  ✓ Installed and started!")
+	fmt.Println()
+	fmt.Println("  Manage with:")
+	fmt.Println("    systemctl --user status unarr")
+	fmt.Println("    systemctl --user restart unarr")
+	fmt.Println("    journalctl --user -u unarr -f")
+	fmt.Println()
+
+	return nil
+}
+
+func installLaunchd(data serviceData, green *color.Color) error {
+	os.MkdirAll(data.LogDir, 0o755)
+
+	dir := filepath.Join(data.Home, "Library", "LaunchAgents")
+	os.MkdirAll(dir, 0o755)
+
+	path := filepath.Join(dir, "com.torrentclaw.unarr.plist")
+	f, err := os.Create(path)
+	if err != nil {
+		return fmt.Errorf("create plist: %w", err)
+	}
+	defer f.Close()
+
+	tmpl := template.Must(template.New("launchd").Parse(launchdTemplate))
+	if err := tmpl.Execute(f, data); err != nil {
+		return fmt.Errorf("write plist: %w", err)
+	}
+
+	fmt.Printf("  Created: %s\n", path)
+
+	exec.Command("launchctl", "load", path).Run()
+
+	fmt.Println()
+	green.Println("  ✓ Installed and loaded!")
+	fmt.Println()
+	fmt.Println("  Manage with:")
+	fmt.Println("    launchctl list | grep unarr")
+	fmt.Println("    launchctl unload " + path)
+	fmt.Println("    tail -f " + filepath.Join(data.LogDir, "unarr.log"))
+	fmt.Println()
+
+	return nil
+}
+
+func runDaemonUninstall() error {
+	home, _ := os.UserHomeDir()
+
+	bold := color.New(color.Bold)
+	green := color.New(color.FgGreen)
+
+	fmt.Println()
+	bold.Println("  unarr daemon uninstall")
+	fmt.Println()
+
+	switch runtime.GOOS {
+	case "linux":
+		exec.Command("systemctl", "--user", "stop", "unarr").Run()
+		exec.Command("systemctl", "--user", "disable", "unarr").Run()
+		path := filepath.Join(home, ".config", "systemd", "user", "unarr.service")
+		os.Remove(path)
+		exec.Command("systemctl", "--user", "daemon-reload").Run()
+		green.Printf("  ✓ Removed %s\n", path)
+
+	case "darwin":
+		path := filepath.Join(home, "Library", "LaunchAgents", "com.torrentclaw.unarr.plist")
+		exec.Command("launchctl", "unload", path).Run()
+		os.Remove(path)
+		green.Printf("  ✓ Removed %s\n", path)
+
+	default:
+		return fmt.Errorf("service uninstall not supported on %s yet", runtime.GOOS)
+	}
+
+	fmt.Println()
+	return nil
+}
+